Engine stalling added. Electric IdleRPMs set to 0 to keep them from stalling.

The RPM has been unlocked so it can go below idle and engines will now stall if the RPM goes too low. This was discussed at length a while (read "months") ago and was closed due to the assessed amount of work required for this fix. The code is here, but this brings a significant gameplay change, so it may require additional discussion before pulling to master.